1. Field of the Invention
The present invention relates to a drug-releasing stent which is inserted into a narrowed blood vessel to dilate the blood vessel and slowly releases a drug in the blood vessel, which is manufactured by coating the surface of the stent with titanium oxide, modifying the surface of the coated film, and chemically attaching the drug thereto.
2. Description of Related Art
A stent is a medical device inserted into a blood vessel narrowed due to various diseases to dilate the blood vessel and improve blood circulation. In general, the stent is inserted in heart blood vessels, aorta or brain blood vessels along with a balloon catheter, and the balloon is inflated to expand the coronary passage. As the balloon inflates, the stent expands outward and restores the blood vessel passage to its original state. Accordingly, the existing stent requires elasticity and ductility. That is to say, the stent requires ductility because it has to be inserted into complex and twisted passages. Further, upon insertion, elasticity is required to prevent deformation of the stent structure by the force applied from blood vessel tissues. For these reasons, corrosion-resistant stainless steel has been used to manufacture the stent. Although the introduction of metal-based stents avoids acute vessel closure and reduces restenosis after balloon angioplasty, restenosis in the stent resulting from neointimal hyperplasia during the restoration of the damaged blood vessel is becoming a problem. As an effort to prevent the restenosis, a drug is provided in the stent, so that the drug is supplied into the blood vessel after the insertion of the stent. This drug therapy inhibits cell proliferation and, thereby, supresses neointimal hyperplasia.
Meanwhile, recently, a technique of coating an aluminum thin film on the surface of a stainless steel stent, oxidizing the aluminum film to form a nanostructure having multiple pores, and injecting a drug into the pores in order to prevent restenosis in the blood vessel was disclosed in Korean Patent Publication No. 10-2004-0011463.
Since the stent inserted in the blood vessel is in direct contact with the blood vessel tissues, the surface of the stent should not be harmful to the human body. Further, a special technique is required to inject the drug into the stent.
Drug-releasing stents with organic compounds coated on the surface and drugs attached thereto are disclosed in Korean Patent Application No. 10-2005-0004331, Korean Patent Publication No. 10-2003-0020476 and others. However, the safety of the organic compound coated film has not been confirmed yet in terms of blood compatibility, cytotoxicity, or the like. In contrast, titanium oxide is biologically and biochemically safe and is widely used for cosmetics, food additives, or the like.